This application relates to an image reader that reads an image on a document and generates image data on the basis of the image and a method of reading an image.
In an image reader that incorporates an automatic document feeder, such as a copier or a facsimile machine, a document placed on a document tray is automatically transported to an image-reading position, and is discharged from the image reader after an image on the document is read. Alternatively, in a flatbed-type image reader, a document is placed on a platen glass with a side to be read down, and an image of the document is read by an image-reading unit that moves under the platen glass.
These image readers have sheet sensors in the vicinity of a position where the document is placed. The sheet sensors detect the document placed on the document tray or the platen glass by a user, and the sheet size of the document is specified on the basis of a detection signal from the sheet sensors. Japanese Patent Laid-Open No. 11-088615 discloses one such image reader.
In the aforementioned image readers, however, a number of sheet sensors must be provided to specify various sheet sizes of documents. This will complicate the configuration of the image reader and cause an increase in production costs.